Product Information for Olmetec (olmesartan medoxomil)



APPROVED PRODUCT INFORMATION

OLMETEC(

(olmesartan medoxomil)

NAME OF THE MEDICINE

OLMETEC (olmesartan medoxomil), a prodrug, is hydrolyzed to olmesartan during absorption from the gastrointestinal tract. Olmesartan is a selective AT1 subtype angiotensin II receptor antagonist.

Olmesartan medoxomil (CAS no. 144689-63-4) is described chemically as 2,3-dihydroxy-2-butenyl 4-(1-hydroxy-1-methylethyl)-2-propyl-1-[p-(o-1H-tetrazol-5-ylphenyl)benzyl] imidazole-5-carboxylate, cyclic 2,3-carbonate.

Its empirical formula is C29H30N6O6 and its structural formula is:

DESCRIPTION

Olmesartan medoxomil is a white to light yellowish-white powder or crystalline powder with a molecular weight of 558.59. It is practically insoluble in water and sparingly soluble in methanol. OLMETEC is available for oral use as film-coated tablets containing 10 mg, 20 mg, or 40 mg olmesartan medoxomil. OLMETEC tablets also contain the following inactive ingredients: microcrystalline cellulose, low-substituted hydroxypropylcellulose, lactose, hydroxypropylcellulose, magnesium stearate, and Opadry OY-S-38956 that contains titanium dioxide, talc, and hydroxypropylmethylcellulose.

OLMETEC extemporaneous suspension contains additional inactive ingredients: purified water, Ora-Sweet® (syrup vehicle) and Ora-Plus® (suspending vehicle). Ora-Sweet® contains citric acid, flavouring, glycerine, methylparaben, potassium sorbate, sodium phosphate, sorbitol, sucrose, and purified water. Ora-Plus® contains calcium sulphate, carrageenan, citric acid, dimethicone antifoam emulsion, methylparaben, microcrystalline cellulose, sodium carboxymethylcellulose, potassium sorbate, sodium phosphate monobasic, trisodium phosphate, xanthan gum, and purified water.

PHARMACOLOGY

Pharmacodynamics

Angiotensin II is formed from angiotensin I in a reaction catalyzed by angiotensin converting enzyme (ACE, kininase II). Angiotensin II is the principal pressor agent of the renin-angiotensin system, with effects that include vasoconstriction, stimulation of synthesis and release of aldosterone, cardiac stimulation and renal reabsorption of sodium. Olmesartan medoxomil is an orally active angiotensin II receptor (type AT1) antagonist. It has more than a 12,500-fold greater affinity for the AT1 receptor than for the AT2 receptor. It is expected to block all actions of angiotensin II mediated by the AT1 receptor, regardless of the source or route of synthesis of angiotensin II. The selective antagonism of the angiotensin II (AT1) receptors results in increases in plasma renin levels and angiotensin I and II concentrations, and some decrease in plasma aldosterone concentrations.

Angiotensin II plays a significant role in the pathophysiology of hypertension via the type 1 (AT1) receptor.

In hypertension, olmesartan medoxomil causes a dose-dependent, long-lasting reduction in arterial blood pressure. There has been no evidence of first-dose hypotension, of tachyphylaxis during long-term treatment, or of rebound hypertension after cessation of therapy.

Once daily dosing with olmesartan medoxomil provides an effective and smooth reduction in blood pressure over the 24-hour dose interval. Once daily dosing produced similar decreases in blood pressure as twice daily dosing at the same total daily dose.

With continuous treatment, maximum reductions in blood pressure are achieved by 8 weeks after the initiation of therapy, although a substantial proportion of the blood pressure lowering effect is already observed after 2 weeks of treatment. When used together with hydrochlorothiazide, the reduction in blood pressure is additive and coadministration is well tolerated.

The effect of olmesartan on mortality and morbidity is not yet known.

Pharmacokinetics

Absorption

Olmesartan medoxomil is a prodrug. It is rapidly converted to the pharmacologically active metabolite, olmesartan, by esterases in the gut mucosa and in portal blood during absorption from the gastrointestinal tract.

No intact olmesartan medoxomil or intact side chain medoxomil moiety have been detected in plasma or excreta. The mean absolute bioavailability of olmesartan from a tablet formulation was 25.6%.

The mean peak plasma concentration (Cmax) of olmesartan is reached within about 2 hours after oral dosing with olmesartan medoxomil, and olmesartan plasma concentrations increase approximately linearly with increasing single oral doses up to about 80 mg.

Food has minimal effect on the bioavailability of olmesartan and therefore olmesartan medoxomil may be administered with or without food.

Distribution

The mean volume of distribution after intravenous dosing is in the range of 16–29 litres. Olmesartan is highly bound to plasma proteins (99.7%), but the potential for clinically significant protein binding displacement interactions between olmesartan and other highly bound coadministered drugs is low (as confirmed by the lack of a clinically significant interaction between olmesartan medoxomil and warfarin). The binding of olmesartan to blood cells is negligible.

In rats, olmesartan crossed the blood-brain barrier poorly, if at all. Olmesartan crossed the placental barrier in rats and was distributed to the foetus. Olmesartan was distributed to milk at low levels in rats.

Metabolism

Following the rapid and complete conversion of olmesartan medoxomil to olmesartan during absorption, there is virtually no further metabolism of olmesartan.

Elimination

Total plasma clearance was typically 1.3 L/h (CV, 19%) and was relatively slow compared with hepatic blood flow (approximately 90 L/h). Approximately 30% to 50% of the systemically absorbed drug is excreted in the urine whilst the remainder is excreted in faeces (via the bile).

The terminal elimination half-life of olmesartan varied between 10 and 15 hours after multiple oral dosing. Steady state was reached after the first few doses and no further accumulation was evident after 14 days of repeated dosing. Renal clearance was approximately 0.5–0.7 L/h and was independent of dose.

Pharmacokinetics in special populations

Elderly

In hypertensive patients, the AUC at steady state was increased by approximately 33% in elderly patients (65–75 years old) and by approximately 31% (adjusted for gender and body mass index) in very elderly patients ((75 years old) compared with the younger age group.

Paediatric

The single-dose pharmacokinetics of olmesartan was investigated in an open-label study in paediatric hypertensive patients aged 1 to 16 years. Refer to Table 1 for a summary of PK parameters. The clearance of olmesartan in paediatric patients was similar to that in adult patients when adjusted by body weight. There are, however, very limited data on the pharmacokinetics of olmesartan in children less than 6 years (see PRECAUTIONS, Paediatric Use).

Table 1. Mean plasma pharmacokinetic parameters of olmesartan in paediatric hypertension patients1

|Parameter; mean (SD) |6-12 Year Age Group (n=10) |13-16 Year Age Group (n=10) |

|Cmax (ng/mL) |1227 (451) |895 (262) |

|AUC0-t (ng/mL*hr) |7874 (2913) |5851 (2083) |

|AUC0-∞ (ng/mL*hr) |7988 (2913) |5982 (2130) |

|Tmax (hr) |2.8 (1.3) |2.5 (1.1) |

|t1/2 (hr) |8.4 (2.4) |9.1 (1.9) |

|CL/F (L/hr) |4.3 (1.9) |6.1 (2.6) |

|1 Sample size insufficient to support calculation of summary statistics in 2-5 year age group (n=4) |

Gender

Minor differences were observed in the pharmacokinetics of olmesartan in women compared with men. AUC and Cmax were 10–15% higher in women than in men.

Renal impairment

In patients with renal insufficiency, serum concentrations of olmesartan were elevated compared with subjects with normal renal function. After repeated dosing, the AUC was approximately tripled in patients with severe renal impairment (creatinine clearance ................
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